Tech Tip Fix: Volkswagen A/C Clutch Control Testing Manual A/C Systems using Fan Control Modules with 14 Pin and 4 Pin Connection Connectors

WORLDPAC Assist presents Tech Tip Fix, a WIN (WORLDPAC Industry News) Tech Tip series based on fixes available from WORLDPAC Assist.

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Volkswagen A/C Clutch Control Testing Manual A/C Systems using Fan Control Modules with 14 pin and 4 pin connection connectors

by Jim Newkirk, WORLDPAC Assist European Team Leader

In this example a 2002 Volkswagen Beetle 2.0L AVH with manual climate control was experiencing two separate problems.

The Air Conditioning Compressor Clutch would not engage

The Cooling Fans would not operate at any speed

Diagnostic Procedures:

1. When the A/C is switched on (the blower motor must also be running at any speed) check for 12 volts from the A/C switch in the dash to the fan control module pin T14/8.
   
   NOTE: Cooling fans should run at low speed whenever the A/C is switched on.



2. Check for voltage to the compressor clutch via pin T14/10. If voltage is present proceed with clutch and/or wiring diagnosis. If a pulsed voltage is present, look for a shorted compressor clutch.



3. Check for good ground to pin T14/6.



4. Check for 12 volts to pin T14/9 when the ignition is in the "on" position.



5. Check for 12 volts to pin T14/4 via fuse #16 at all times. (Failure of this power supply can cause the cooling fans to run at high speed at all times).



6. Check for 12 volts to pin T4a/1 and T4a/3 via fuses S164 and S180 respectively at all times.


The fuses are located in the battery fuse box and have been a common failure point for the A/C system. Be sure to inspect the fuse box for heat damage or poor/loose connections.

NOTE: It is critical to remove the battery fuse box and inspect all fuses and connections (from both top and bottom) for damage.


7. Check for approximately 35% duty cycle from the A/C high pressure sensor at pin T14/2 with the ignition on but the compressor not running (duty cycle will increase as the high side pressure increases.
   
   NOTE: this is a ground side duty circuit. If tested with the positive lead of the DVOM to pin T14/2 a reading of 70% duty will be indicated. This is a normal reading when testing in this manner.
   
   A duty cycle above 90% or below 20% will command the compressor off and would indicate a faulty pressure sensor with the compressor not running and the refrigerant levels normal.



8. Disconnect the 14-pin connector and verify continuity between pin T14/14 and T14/5. This checks the ambient switch (open circuit below 32 degrees F).



9. Disconnect the 14-pin connector. Using a fused 12-volt jumper, apply power to pin T14/10. Compressor clutch should engage. Reconnect the 14-pin connector.



10. Check for voltage at pin T14/13. This voltage signal comes from the Instrument panel and will normally vary from approximately 5 to 11 volts. If the temperature gauge in the Instrument panel detects an overheat condition it will ground this pin to shut off the compressor and run the cooling fans at high speed.



11. Check for 11-volt reference voltage at pin T14/3 (the Powertrain Control Module (PCM) will ground this reference to request compressor shutdown for a Wide Open Throttle (WOT) condition).
    
    It is important to note that any problems with any other circuits at the fan module will cause loss of this voltage signal.



12. If all tests pass, the Fan Control Module (FCM) is faulty and must be replaced.

After performing the diagnostic procedures, poor/burned connections were discovered at the Battery Fuse Box.

Replacing the damaged Battery Fuse Box restored proper voltage to the Fan Control Module and restored both A/C Compressor and Cooling Fan Operation.

This Tech Tip Fix was performed and documented by Jim Newkirk, WORLDPAC Assist European Team Leader.

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Tech Tip Fix: Volkswagen Diesel Dynamic Pump Timing 1.9L TDI ALH Diesel Engines

WORLDPAC Assist presents Tech Tip Fix, a WIN (WORLDPAC Industry News) Tech Tip series based on fixes available from WORLDPAC Assist.

WORLDPAC Assist offers the largest source of Confirmed Fixes documented by 41 factory trained ASE certified master technicians. Over 1000 new problems with tests and fixes are added to WORLDPAC Assist each week.

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Volkswagen Diesel Dynamic Pump Timing 1.9L TDI ALH Diesel Engines

by Steve Griff, WORLDPAC Assist European Specialist

In this example a 2003 Volkswagen Jetta with Engine 1.9L TDI ALH had a timing belt replaced and resetting of the Injection Pump Dynamic Timing was performed.

Diagnostic Procedures:

NOTE: When any work is performed on a 1.9L TDI diesel that involves the timing belt, Dynamic Injection Pump Start of Injection Timing must be checked and adjusted as necessary.

1. It is strongly recommended that the proper cam and pump locking tools are used when servicing the timing belt. Incorrect timing can easily occur if the lock down tools is not used. The VW 3418 Cam Jig and the VW 3359 Pump Locating Pin should be used.



2. Once the basic mechanical timing is set using the lock down tools, a full function VW compatible scan tool is required to set the dynamic pump timing.



3. Dynamic timing specification is based off actual fuel temperature while the engine is running.



4. Use the scan tool to enter Engine Address Word 01, Function 04 Basic settings and Display Group 000. 10 Data fields will be displayed. Display field 2 indicates the actual Dynamic Pump Start of Injection Timing. Display Field 9 indicates current fuel temperature.



5. With the engine running at idle check the value in Field 2. Typically a value of about 65 at an indicated fuel temperature in field 9 of 90 is normal.
   
   NOTE: For every 10 degrees hotter than 90 in field 9 subtract 2 from field 2 to calculate the normal timing value. For every 10 degrees cooler than 90 in field 9 add 2 to the value in field 2 to calculate normal timing value.



6. If the value in field 2 is not correct, shut off the engine and adjust timing by loosening the 3 bolts at the pump gear until the center shaft can be moved
   
   NOTE: Moving the center shaft to the left advances timing and raises the timing number in field 2; moving the center shaft to the right retards timing and lowers the number in field 2.
   
   UNDER NO CIRCUMSTANCES LOOSEN THE CENTER BOLT!
   
   If the center bolt is loosened the internal pump timing is changed and the pump must be retimed on a test bench!



7. Small movements will cause large changes in pump timing so be careful.



8. Once timing is correctly set, retighten the 3 pump bolts, restart the engine and re-verify correct dynamic timing numbers.

After performing the timing procedures normal vehicle operation was restored.

This Tech Tip Fix was performed and documented by Steve Griff, WORLDPAC Assist European Specialist.

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